A polyalkylene carbonate is an amorphous transparent resin, and has only an aliphatic structure, unlike an aromatic carbonate which is a similar engineering plastic, and is synthesized by a copolymerization reaction under a catalyst by using carbon dioxide and an epoxide as a monomer. Such a polyalkylene carbonate is advantageous in being excellent in transparency, elongation and oxygen blocking properties, exhibiting biodegradation, and being completely decomposed into carbon dioxide and water during burning, thus leaving no carbon residue.
Accordingly, various catalysts are being studied and suggested in order to produce such a polyalkylene carbonate resin. As a typical catalyst, there has been known a zinc dicarboxylate-based catalyst such as a glutarate catalyst in which zinc and a dicarboxylic acid are bonded.
Such a zinc dicarboxylate-based catalyst is produced in the form of a nanometer scale powder by reacting a zinc precursor with the dicarboxylic acid, and the powdery catalyst forms an agglomerate having a considerable size, so that the surface area thereof is reduced in the production of the polyalkylene carbonate resin, and the catalyst activation may be lowered.
In addition, the conventionally known zinc dicarboxylate-based catalyst has a selectivity of 95% for a polyalkylene carbonate polymerization product, and when the polymerization is performed using the catalyst, a by-product such as alkylene carbonate in addition to the polyalkylene carbonate is generated. For this reason, an additional process is required in order to remove the by-product after polymerization.
In addition, the conventional zinc dicarboxylate-based catalyst causes depolymerization of the polyalkylene carbonate resin polymerized by a backbiting reaction, so that it is necessary for the catalyst to be removed from the resin after completion of the polymerization. From this reason, a method in which an additional flocculant is added, and then physically removed by using a filter or chemically removed by using an ion exchange resin may be used. However, the removal of the zinc dicarboxylate-based catalyst using these methods requires a method in which an additional solvent is added to lower a viscosity, and then the catalyst is removed, followed by removing the solvent, so that a large amount of energy may be consumed, and the catalyst used in polymerization may be difficult to be reused.
Due to this, there is being continuously required a zinc dicarboxylate-based catalyst which may be capable of being used repeatedly or continuously by having a large reaction surface area and a high selectivity to the polymerization reaction product and being easily recoverable.